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to 10.0.31.1 via t1-0/0/3.0<br />

10.0.29.0/24 *[BGP/170] 01:19:38, localpref 100<br />

AS path: 65505 I<br />

> to 10.0.31.1 via t1-0/0/3.0<br />

10.0.31.0/24 [BGP/170] 15:23:37, localpref 100<br />

AS path: 65505 I<br />

> to 10.0.31.1 via t1-0/0/3.0<br />

172.19.121.0/24 [BGP/170] 15:23:37, localpref 100<br />

AS path: 65505 I<br />

> to 10.0.31.1 via t1-0/0/3.0<br />

192.168.11.1/32 *[BGP/170] 01:18:52, MED 1, localpref 100<br />

AS path: 65505 I<br />

> to 10.0.31.1 via t1-0/0/3.0<br />

192.168.14.1/32 *[BGP/170] 15:23:37, localpref 100<br />

AS path: 65505 I<br />

> to 10.0.31.1 via t1-0/0/3.0<br />

192.168.18.1/32 *[BGP/170] 01:23:38, MED 65, localpref 100<br />

AS path: 65505 I<br />

> to 10.0.31.1 via t1-0/0/3.0<br />

The BGP routes in the routing table now include the value of the BGP multiple exit<br />

discriminator (MED) attribute that was advertised with the prefix:<br />

192.168.11.1/32 *[BGP/170] 01:18:52, MED 1, localpref 100<br />

AS path: 65505 I<br />

> to 10.0.31.1 via t1-0/0/3.0<br />

192.168.18.1/32 *[BGP/170] 01:23:38, MED 65, localpref 100<br />

AS path: 65505 I<br />

> to 10.0.31.1 via t1-0/0/3.0<br />

The output shows the MED in the prefixes to the IBGP routers in the immediately<br />

adjacent AS. The MED is the BGP metric and is used as a tie-breaker to pick the path<br />

to an AS when there are multiple equivalent paths between the ASs and when all<br />

other factors in determining the exit point are equal.<br />

The show bgp group command shows information about the two BGP groups on the<br />

router:<br />

aviva@RouterF> show bgp group<br />

Group Type: External Local AS: 65500<br />

Name: session-to-AS65505 Index: 0 Flags: <br />

Export: [ send-statics ]<br />

Total peers: 1 Established: 1<br />

10.0.31.1+179<br />

inet.0: 5/8/0<br />

Group Type: Internal AS: 65500 Local AS: 65500<br />

Name: internal-within-AS65500 Index: 1<br />

Flags: <br />

Total peers: 2 Established: 2<br />

192.168.15.1+179<br />

192.168.17.1+179<br />

inet.0: 0/0/0<br />

Groups: 2 Peers: 3 External: 1 Internal: 2 Down peers: 0 Flaps: 0<br />

Table Tot Paths Act Paths Suppressed History Damp State Pending<br />

inet.0 8 5 0 0 0 0<br />

Configuring BGP on Routers Within an AS | 435<br />

This is the Title of the Book, eMatter Edition<br />

Copyright © 2008 O’Reilly & Associates, Inc. All rights reserved.

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